Foil bearing

ABSTRACT

The invention relates to a foil bearing ( 10 ) having at least one foil ( 16, 18 ), which is arranged and fixed in place inside a bearing bushing ( 12 ). In order to simply the production, in particular assembly, of the foil bearing ( 10 ), the bearing bushing ( 12 ) has at least two openings ( 20, 22, 24 ) offset from each other in the circumferential direction of the bearing bushing ( 12 ) or depressions ( 120, 122, 124 ) made in the inner lateral surface of the bearing bushing, into which openings or depressions two opposing circumferential end sections ( 16   a,    16   b,    18   a,    18   b ) of the at least one foil ( 16, 18 ) engage.

BACKGROUND OF THE INVENTION

The invention relates to a foil bearing having at least one foil whichis arranged and fixed inside a bearing bushing.

A foil bearing of this kind is known from EP 0 927 831 A1. This foilbearing has a bearing bushing, within which at least one foil, which isfixed in the bearing bushing, is arranged. In order to fix the at leastone foil, the bearing bushing has on its inner lateral surface T-shapedwebs which extend in the direction of the longitudinal axis of thebearing bushing. The at least one foil is inserted by itscircumferential end sections in each case under one of the T-shaped websand is then fixed in the circumferential direction between two adjacentwebs. The production of the bearing bushing with the T-shaped webs iscomplex since the bearing bushing has to be machined on its innerlateral surface in order to do this. As a result, the foil bearing isalso expensive to produce.

SUMMARY OF THE INVENTION

The foil bearing according to the invention has the advantage thatfixing of the at least one foil is made possible in a simple manner. Theproduction of the depressions or openings is possible in a very simplemanner, and therefore the foil bearing can be produced at low cost.

Advantageous embodiments and developments of the invention are specifiedin the dependent claims.

The fixing of the at least one foil is further improved by the designaccording to the invention. The design of the openings as bores makes itpossible to produce the bearing bushing in a particularly simple mannersince it does not have to be machined on its inner lateral surface.Other embodiments according to the invention enable reliable fixing ofthe at least one foil, both in the radial direction and in the directionof the longitudinal axis of the bearing bushing.

Further advantages, features and details of the invention will be foundin the following description, in which various exemplary embodiments ofthe invention are described in detail with reference to the drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the invention is illustrated in the drawingand explained in greater detail in the following description.Specifically:

FIG. 1 shows a foil bearing in a cross section with a bearing bushingand foils arranged therein,

FIG. 2 shows the bearing bushing in cross section without foils,

FIG. 3 shows the bearing bushing in a side view,

FIG. 4 shows a foil in an initial state before being arranged in thebearing bushing,

FIG. 5 shows a segment of the foil from FIG. 4 in a modified embodiment,and

FIG. 6 shows a segment of the foil from FIG. 4 in a further modifiedembodiment.

DETAILED DESCRIPTION

FIGS. 1 to 6 illustrate a foil bearing 10 with a hollow-cylindricalbearing bushing 12. The bearing bushing 12 is also referred to as abearing ring and essentially has the shape of a straight, hollowcircular cylinder with a longitudinal axis 14. Two foils 16, 18 of thefoil bearing 10 are arranged in the interior of the bearing bushing 12.The foil 16 is also referred to as a beam, bump or lower foil and isarranged between the bearing bushing 12 and the foil 18, which is alsoreferred to as a top foil or upper foil. The foil bearing 10 serves forthe rotatable mounting of a shaft (not illustrated), which rests againstthe foil 18.

The bearing bushing 12 has openings 20, 22, 24, illustrated in FIGS. 1to 3, in its lateral surface which form a geometry for fixing the foils16, 18 in the bearing bushing 12. The openings 20, 22, 24 are preferablydesigned as bores, which are introduced into the bearing bushing 12 fromthe outside. The openings 20, 22, 24 each have a diameter d.

As illustrated in FIG. 3, the two openings 20, 22, which are referred tobelow as the first opening 20 and the second opening 22, are arrangedoffset with respect to one another in the direction of the longitudinalaxis 14 of the bearing bushing 12 on a line L parallel to thelongitudinal axis 14. Opening 24 is referred to below as the thirdopening 24 and is arranged offset with respect to the first and secondopenings 20, 22 in the circumferential direction of the bearing bushing12. As illustrated in FIG. 2, there is an angle α between the first andsecond openings 20, 22 and the third opening 24 with respect to thelongitudinal axis 14 of the bearing bushing 12. When viewed in thedirection of the longitudinal axis 14 of the bearing bushing 12, thethird opening 24 is preferably arranged between the first opening 20 andthe second opening 22, in particular at least approximately centrallybetween the first opening 20 and the second opening 22, as illustratedin FIG. 3. The first opening 20 and the second opening 22 are arrangedin a first circumferential position of the bearing bushing 12, and thethird opening 24 is arranged in a second circumferential position of thebearing bushing 12.

Instead of the through openings 20, 22, 24, depressions 120, 122, 124can also be provided in the inner lateral surface of the bearing bushing12, as is illustrated by dashed lines in the lower region of the bearingbushing 12 in FIG. 2. However, these depressions 120, 122, 124 must beintroduced from the interior of the bearing bushing 12 and may bedesigned as countersinks, for example.

In FIG. 4, the foils 16, 18 are shown in an unwound state before theyare arranged within the bearing bushing 12. On their two oppositecircumferential end sections 16 a, 18 a and 16 b, 18 b pointing in thecircumferential direction, the foils 16, 18 each have at least oneinsertion tab 26, which each have a smaller width b than the width B ofthe foils 16, 18 in the direction of the longitudinal axis 14 of thebearing bushing 12. There are two insertion tabs 26 arranged offset withrespect to one another in the direction of the longitudinal axis 14 onone circumferential end section 16 a, 18 a of the foils 16, 18, andthere is only one insertion tab 26 on the other circumferential endsection 16 b, 18 b of the foils 16, 18. Provision can also be made forjust one insertion tab 26 or in each case a plurality, also more thantwo, insertion tabs 26 to be present on both circumferential endsections of the foils.

The insertion tabs 26 are preferably designed in such a way that theytaper toward their free ends, that is to say their width b decreases. Asillustrated in FIG. 4, the insertion tabs 26 can be of at leastapproximately trapezoidal design. Alternatively, as illustrated in FIG.5, the insertion tabs 26 can also be of approximately triangular ortooth-shaped design or, as illustrated in FIG. 6, approximatelyrectangular with rounded ends.

The foils 16, 18 with the insertion tabs 26 can be designed, forexample, as metal foils and can be produced by punching. A third foilcan also be arranged between the two foils 16, 18.

In order to arrange the foils 16, 18 within the bearing bushing 12, theyare rolled up to a diameter which is smaller than the inside diameter ofthe bearing bushing 12 and introduced into the bearing bushing 12 in thedirection of the longitudinal axis 14. The insertion tabs 26 present onthe circumferential end section 16 a, 18 a of the foils 16, 18 areintroduced into the first opening 20 or second opening 22 of the bearingbushing 12, and the insertion tab 26 of the other circumferential endsection 16 b, 18 b of the foils 16, 18 is introduced into the thirdopening 24 of the bearing bushing 12. During this process, the foils 16,18 spring apart in the circumferential direction of the bearing bushing12, and the insertion tabs 26 hook into the openings 20, 22, 24, as aresult of which the foils 16, 18 are fixed in the bearing bushing 12 inthe radial direction and in the direction of the longitudinal axis 14.Since the insertion tabs 26 are arranged offset with respect to oneanother in the direction of the longitudinal axis 14, they do notcollide with one another and they can be introduced into the openings20, 22, 24.

The size of the angle α and of the diameter d of the openings 20, 22,24, as well as the width b of the insertion tabs 26, are suitablydetermined in order to enable secure retention of the insertion tabs 26in the openings 20, 22, 24 and thus secure fixing of the foils 16, 18.

The shaft belongs, for example, to a rotor (likewise not illustrated) ofa turbomachine. The turbomachine is, for example, part of an air supplyunit in a fuel cell system. In the fuel cell system, the turbomachine isdesigned, for example, as a compressor. The compressor comprises acompressor wheel, which is an advantageous component of the rotor.

1. A foil bearing (10) having at least one foil (16, 18), which isarranged and fixed inside a bearing bushing (12), characterized in thatthe bearing bushing (12) has at least two openings (20, 22, 24) arrangedoffset with respect to one another in a circumferential direction of thebearing bushing (12), or has at least two depressions (120, 122, 124)made in an inner lateral surface of the bearing bushing, into whichopenings or depressions two opposite circumferential end sections (16 a,16 b, 18 a, 18 b) of the at least one foil (16, 18) engage.
 2. The foilbearing as claimed in claim 1, characterized in that at least twoopenings (20, 22) or depressions (120, 122) are arranged offset withrespect to one another in a direction of a longitudinal axis (14) of thebearing bushing (12).
 3. The foil bearing as claimed in claim 2, whereinthe at least two openings include a first opening (20), a second opening(22) and a third opening (24), wherein the at least two depressionsinclude a first depression (120), a second depression (122) and a thirddepression (124), wherein, in a first circumferential position, thefirst opening (20) or the first depression (120) is provided, and, inthe direction of the longitudinal axis (14) of the bearing bushing (12),the second opening (22) or the second depression (122) is provided, saidsecond opening or second depression being offset with respect to thefirst opening (20) or first depression (120), and wherein, in a secondcircumferential position, the third opening (24) or third depression(124) is provided, the third opening or third depression being offsetwith respect to the first and second openings (20, 22) or depressions(120, 122) in the direction of the longitudinal axis (14) of the bearingbushing (12).
 4. The foil bearing as claimed in claim 3, characterizedin that, when viewed in the direction of the longitudinal axis (14) ofthe bearing bushing (12), the third opening (24) or depression (124) isarranged between the first opening (20) or depression (120) and thesecond opening (22) or depression (122).
 5. The foil bearing as claimedin claim 1, characterized in that the at least two openings (20, 22, 24)are bores.
 6. The foil bearing as claimed in claim 1, characterized inthat the at least two depressions (120, 122, 124) are countersinks. 7.The foil bearing as claimed in claim 1, characterized in that at leastone of the circumferential end sections (16 a, 16 b, 18 a, 18 b) of theat least one foil (16, 18) has at least one insertion tab (26), whichengages in at least one of the at least two openings (20, 22, 24) or atleast two depressions (120, 122, 124).
 8. The foil bearing as claimed inclaim 7, characterized in that the at least one insertion tab (26)tapers in the circumferential direction toward a free end.
 9. The foilbearing as claimed in claim 8, characterized in that the at least oneinsertion tab (26) is at least approximately trapezoidal or triangularor rectangular with a rounded end.
 10. The foil bearing as claimed inclaim 8, characterized in that the at least one foil (16, 18) includesan upper foil (18) and a lower foil (16), which is arranged between theupper foil (18) and the bearing bushing (12).
 11. The foil bearing asclaimed in claim 1, wherein the bearing bushing (12) has the at leasttwo openings (20, 22, 24) arranged offset with respect to one another inthe circumferential direction of the bearing bushing (12), into whichopenings the two opposite circumferential end sections (16 a, 16 b, 18a, 18 b) of the at least one foil (16, 18) engage.
 12. The foil bearingas claimed in claim 11, characterized in that at least two openings (20,22) are arranged offset with respect to one another in a direction of alongitudinal axis (14) of the bearing bushing (12).
 13. The foil bearingas claimed in claim 12, wherein the at least two openings include afirst opening (20), a second opening (22) and a third opening (24),wherein, in a first circumferential position, the first opening (20) isprovided, and, in the direction of the longitudinal axis (14) of thebearing bushing (12), the second opening (22) is provided, said secondopening being offset with respect to the first opening (20), andwherein, in a second circumferential position, the third opening (24) isprovided, the third opening being offset with respect to the first andsecond openings (20, 22) in the direction of the longitudinal axis (14)of the bearing bushing (12).
 14. The foil bearing as claimed in claim 1,wherein the bearing bushing (12) has the at least two depressions (120,122, 124) made in an inner lateral surface of the bearing bushing, intowhich depressions the two opposite circumferential end sections (16 a,16 b, 18 a, 18 b) of the at least one foil (16, 18) engage.
 15. The foilbearing as claimed in claim 14, characterized in that at least twodepressions (120, 122) are arranged offset with respect to one anotherin a direction of a longitudinal axis (14) of the bearing bushing (12).16. The foil bearing as claimed in claim 15, wherein the at least twodepressions include a first depression (120), a second depression (122)and a third depression (124), wherein, in a first circumferentialposition, the first depression (120) is provided, and, in the directionof the longitudinal axis (14) of the bearing bushing (12), the seconddepression (122) is provided, said second depression being offset withrespect to the first depression (120), and wherein, in a secondcircumferential position, the third depression (124) is provided, thethird depression being offset with respect to the first and seconddepressions (120, 122) in the direction of the longitudinal axis (14) ofthe bearing bushing (12).